This invention relates to clamping systems for high and ultra-high vacuum systems.
Vacuum systems find wide applications in research, education, product development, and production. Typical systems are comprised of independent and interchangeable components. Components include testing chambers, pumps, gauges, valves, specimen holders, electron sources, ion sources, photon sources, molecular beam sources, detectors of various types, etc.
Processes or experiments that require high or ultra-high vacuum (UHV) currently employ all metal vacuum joints. A typical all-metal joint, such as that described in U.S. Pat. No. 3,208,758, is illustrated in FIG. 1. Such a joint comprises a flange 20 (FIG. 2) that includes an annular recess 26 and an annular knife edge 30. The flange 20 is intended for mating with another like flange 24 separated by a soft, metallic gasket 34. The opposing knife edges 30, 32 are pressed into the gasket 34 by tightening bolts 38 forming the UHV seal.
In UHV systems, the level of vacuum is dependant upon the speed of the vacuum pumps, the leak rates of the vacuum joints and vacuum walls, the surface area of the chamber and pumping lines, and the surface roughness of the interior components. Cleanliness or purity of the vacuum environment depends upon the interior component""s material, forming method, and surface finish. The practicality of a vacuum system depends on the ease of access for changing specimens, the required down-time to trouble shoot and to do repairs, and the ease with which components may be added and removed from the system. The expense of a vacuum system lies in the cost of components, the required pump types and speeds, and the number and type of extra adapters needed to attach components to a system. Methods of accurately placing testing apparatus, processing equipment, or samples within a system are often required for an experiment or process. The prior art flanges do not adequately optimize some of these requirements, in some cases.
Standard thickness flanges depend on the thickness of the flange to transfer force from the bolts to the sealing gasket in order to crush the gasket and form the seal. This requires that mating flange configurations be one flange with clear bolt holes and one flange with either clear or tapped bolt holes. If both flanges have clear holes, then there must be room for bolt heads on one side of the flange pair and for nuts on the other. If at least one of the flange pairs is not rotatable, then the possible mounting configurations are limited to the number of bolt holes.
Methods for directly attaching two vacuum components that both have tapped holes currently involve one of several options, all of which significantly increase size or complexity of the vacuum system. One method includes inserting an adapter comprised of two flanges on each end of a thin wall tube. Unfortunately, the tube has to be long enough to provide bolt clearance. Another method uses double-sided couplers that bolt to the two components. Such a coupler is described in Crawford U.S. Pat. No. 5,671,956. However, even couplers of this type add length. Adding length and surface area significantly decreases molecular conductance, as well as increasing the overall system size.
A clamping system for a vacuum system comprising a pair of facing flanges to be joined as part of a vacuum system, each having an external mounting groove in the outer perimeter of the flange. Clamp members are attached to the external mounting groove of each of the flanges. Bolts are disposed extending between the clamp members and are configured to draw the clamp members toward each other. The interaction between the clamp member bead and the groove on the flange transmits the closing force from the bolts to a sealing surface on the flange, whereby sufficient compressive force may be generated to create a vacuum tight seal.
Consistent with the present invention, it is possible to insert an additional component or components between two flanges, using only minimal space. The decrease in required space has the advantage of increasing the conductance of the vacuum system. Also, since the present invention does not require modifications to the inserted component or components, industry standard parts may be used in conjunction with the present invention. This last feature is particularly useful in mounting industry standard valves, as opposed to specially modified or specially manufactured valves. Furthermore, because all of the surfaces of the clamp members are machined, and there are no welds, all parts may be fully disassembled. Additionally, it is possible that two vacuum components, both with tapped holes, may be directly attached to each other. Arbitrary angular orientations are possible between non-rotatable flanges. Alternatively, the external mounting grooves of the present invention may be utilized for attachment of support structures or apparatus external to the vacuum system. Because the grooves are symmetric around the perimeter of the flange, support structures may have arbitrary angular orientation with respect to the flange.